Various medical or scientific tests require the preparation of films on transparent slides for microscopic examination. Typically, these films or smears are prepared manually by placing a small amount of fluid, such as blood, cell culture or bone marrow suspension on a microscope slide and pushing or dragging another slide across to form a thin layer. After the slide dries and is treated with a staining solution, a laboratory technician evaluates the film under a microscope. Such manually prepared slides (wedge smears or drag smears) are very technique dependent and produce non-uniform smears or films, with one end too thick, the other end too thin. Additionally, in the case of blood films, the white blood cells are not uniformly distributed across the slide. A superior slide is produced by a slide spinner which consistently distributes a uniform monolayer of cells on a slide.
Prior art slide spinners for preparing blood films disclose a mounting platform for a slide which is able to be rapidly rotated or spun within a containment vessel. Rapid acceleration of the slide causes the blood to be evenly dispersed on the slide. During the short spin cycle, excess blood is flung off the slide into the containment vessel thus forming aerosols.
Use of the prior art devices gives rise to potentially serious health risks related to aerosol borne contagions unless bulky and expensive air filtration systems are employed. In addition to facilitating hazardous aerosol formation, the excess specimen flung off the slides needs to be frequently scrubbed off the containment vessel walls. Even if the containment vessel is lined with absorbent material, it quickly becomes saturated and requires frequent changing. Failure to frequently clean the vessel risks continuing biohazards and creation of a malodor. On occasion slides break, and the glass shards need to be removed along with the residue. These prior art devices thus suffer from aesthetic and biohazard deficits.
Despite having enclosed containment vessels, prior art devices allow for rapid evaporative drying of the film. Thus, care must be taken to ensure spinning is stopped requiring braking systems before the film begins to dry, otherwise there can be artifacts in the film that impair accurate reading. Any buffeting of the cell layer by air turbulence during spinning can also produce artifacts.
Also, while the prior devices may produce a uniform blood film, they do so over the entire slide. No clean area remains for handling and labeling the slide.
Finally, prior art slide spinners have incorporated the use of high power motors with large and heavy, or special purpose, armatures, and commensurately powerful braking systems. This has resulted in spinners which are large and heavy, robbing labs of valuable work space, as well as being mechanically complex, which drove the price of these devices to a point where economic considerations do not favor their use. A practical, compact, cost-effective, safe and effective film preparation device has heretofore been unavailable.